<?php

/*
 * Enano - an open-source CMS capable of wiki functions, Drupal-like sidebar blocks, and everything in between
 * Copyright (C) 2006-2009 Dan Fuhry
 * diffiehellman.php - Diffie Hellman key exchange and supporting functions
 *
 * This program is Free Software; you can redistribute and/or modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for details.
 */

/**
 * EnanoMath GMP backend
 */

class EnanoMath_GMP
{
	var $api = 'GMP';
	
	/**
 	* Initializes a number to a GMP integer.
 	* @param string String representation of the number
 	* @param int Base the number is currently in, defaults to 10
 	* @return resource
 	*/
	
	function init($int, $base = 10)
	{
		return ( is_resource($int) || (is_object($int) && $int instanceof \GMP) ) ? $int : gmp_init($int, $base);
	}
	
	/**
 	* Converts a number from a GMP integer to a string
 	* @param resource
 	* @param int Base, default is 10
 	* @return string
 	*/
	
	function str($int, $base = 10)
	{
		return ( is_string($int) ) ? $int : gmp_strval($int, $base);
	}
	
	/**
 	* Converts a number between bases.
 	* @param resource BigInt to convert
 	* @param int Base to convert from
 	* @param int Base to convert to
 	*/
 	
	function basecon($int, $from, $to)
	{
		return $this->init(gmp_strval(gmp_init($this->str($int), $from), $to));
	}
	
	/**
 	* Generates a random integer.
 	* @param int Length
 	* @return resource
 	*/
	
	function random($len)
	{
		return gmp_random($len / 8);
	}
	
	/**
 	* Powmod operation (calculates (a ^ b) mod m)
 	* @param resource a
 	* @param resource b
 	* @param resource m
 	* @return resource
 	*/
	
	function powmod($a, $b, $m)
	{
		$a = $this->init($a);
		$b = $this->init($b);
		$m = $this->init($m);
		return ( function_exists('gmp_powm') ) ? gmp_powm($a, $b, $m) : gmp_mod(gmp_pow($a, $b), $m);
	}
}

/**
 * EnanoMath big_int backend
 */

class EnanoMath_BigInt
{
	var $api = 'big_int';
	
	/**
 	* Initializes a number to a BigInt integer.
 	* @param string String representation of the number
 	* @param int Base the number is in, defaults to 10
 	* @return resource
 	*/
	
	function init($int, $base = 10)
	{
		return (is_resource($int)) ? $int : bi_from_str($int, $base);
	}
	
	/**
 	* Converts a number from a BigInt integer to a string
 	* @param resource
 	* @param int Base, default is 10
 	* @return string
 	*/
	
	function str($int, $base = 10)
	{
		return ( is_string($int) ) ? $int : bi_to_str($int, $base);
	}
	
	/**
 	* Generates a random integer
 	* @param int Length (bits)
 	* @return resource
 	*/
	
	function random($len)
	{
		return bi_rand($len);
	}
	
	/**
 	* Converts a number between bases.
 	* @param resource BigInt to convert
 	* @param int Base to convert from
 	* @param int Base to convert to
 	*/
	
	function basecon($int, $from, $to)
	{
		return bi_base_convert($this->str($int, $from), $from, $to);
	}
	
	/**
 	* Powmod operation (calculates (a ^ b) mod m)
 	* @param resource a
 	* @param resource b
 	* @param resource m
 	* @return resource
 	*/
	
	function powmod($a, $b, $m)
	{
		$a = $this->init($a);
		$b = $this->init($b);
		$m = $this->init($m);
		return bi_powmod($a, $b, $m);
	}
}

/**
 * EnanoMath BCMath backend
 */

class EnanoMath_BCMath
{
	var $api = 'BCMath';
	
	/**
 	* Initializes a number to a BCMath integer.
 	* @param string String representation of the number
 	* @param int Base the number is in, defaults to 10
 	* @return resource
 	*/
	
	function init($int, $base = 10)
	{
		return $this->basecon($int, $base, 10);
	}
	
	/**
 	* Converts a number from a BCMath integer to a string
 	* @param resource
 	* @param int Base, default is 10
 	* @return string
 	*/
 	
	function str($res)
	{
		return ( is_string($res) ) ? $res : strval($this->basecon($res, 10, $base));
	}
	
	/**
 	* Generates a random integer
 	* @param int Length in bits
 	* @return resource
 	*/
	
	function random($len)
	{
		$len = 4 * $len;
		$chars = '0123456789abcdef';
		$ret = '';
		for ( $i = 0; $i < $len; $i++ )
		{
			$chid = mt_rand ( 0, strlen($chars) - 1 );
			$chr = $chars{$chid};
			$ret .= $chr;
		}
		return $this->basecon($this->init($ret), 16, 10);
	}
	
	/**
 	* Converts a number between bases.
 	* @param resource BigInt to convert
 	* @param int Base to convert from
 	* @param int Base to convert to
 	*/
	
	function basecon($int, $from, $to)
	{
		if ( $from != 10 )
			$int = $this->_bcmath_base2dec($int, $from);
		if ( $to != 10 )
			$int = $this->_bcmath_dec2base($int, $to);
		return $int;
	}
	
	/**
 	* Powmod operation (calculates (a ^ b) mod m)
 	* @param resource a
 	* @param resource b
 	* @param resource m
 	* @return resource
 	*/
	
	function powmod($a, $b, $m)
	{
		$a = $this->init($a);
		$b = $this->init($b);
		$m = $this->init($m);
		return ( function_exists('bcpowmod') ) ? bcpowmod($a, $b, $m) : bcmod( bcpow($a, $b), $m );
	}
	
	// from us.php.net/bc:
	// convert a decimal value to any other base value
	function _bcmath_dec2base($dec,$base,$digits=FALSE) {
			if($base<2 or $base>256) die("Invalid Base: ".$base);
			bcscale(0);
			$value="";
			if(!$digits) $digits=$this->_bcmath_digits($base);
			while($dec>$base-1) {
					$rest=bcmod($dec,$base);
					$dec=bcdiv($dec,$base);
					$value=$digits[$rest].$value;
			}
			$value=$digits[intval($dec)].$value;
			return (string) $value;
	}
	
	// convert another base value to its decimal value
	function _bcmath_base2dec($value,$base,$digits=FALSE) {
			if($base<2 or $base>256) die("Invalid Base: ".$base);
			bcscale(0);
			if($base<37) $value=strtolower($value);
			if(!$digits) $digits=$this->_bcmath_digits($base);
			$size=strlen($value);
			$dec="0";
			for($loop=0;$loop<$size;$loop++) {
					$element=strpos($digits,$value[$loop]);
					$power=bcpow($base,$size-$loop-1);
					$dec=bcadd($dec,bcmul($element,$power));
			}
			return (string) $dec;
	}
	
	function _bcmath_digits($base) {
			if($base>64) {
					$digits="";
					for($loop=0;$loop<256;$loop++) {
							$digits.=chr($loop);
					}
			} else {
					$digits ="0123456789abcdefghijklmnopqrstuvwxyz";
					$digits.="ABCDEFGHIJKLMNOPQRSTUVWXYZ-_";
			}
			$digits=substr($digits,0,$base);
			return (string) $digits;
	}
}

/**
 * Creates a new math object based on what libraries are available.
 * @return object
 */

function enanomath_create()
{
	if ( function_exists('gmp_init') )
		return new EnanoMath_GMP();
	else if ( function_exists('bi_from_str') )
		return new EnanoMath_BigInt();
	else if ( function_exists('bcadd') )
		return new EnanoMath_BCMath();
	else
		throw new Exception('dh_err_not_supported');
}

?>
